1. Field of the Invention
The present invention relates to a digital color copying machine, and more particularly, to a digital color copying machine capable of performing a test mode for making a color adjustment.
2. Description of the Related Art
A conventional digital color copying machine comprises a reading section for reading an image of a document by using a color image sensor and converting the image of the document into image data for printing, and an electrophotographic printer section for printing an image of the document on a copying paper according to the image data. In the case that plural color images are to be superimposed on a copying paper, the document is read out repeatedly by the reading section, and each color image is printed on the same copying paper by the printer section in the order of respective colors predetermined.
The reading section comprises a masking circuit for generating a color-corrected signal corresponding to printing characteristics of the printer section. Generally speaking, it is difficult for the masking process circuit to minimize the color difference between the real document and the copy thereof with respect to all the colors contained therein. Therefore, in such a case that a copy is further copied as a document, the color tone of the secondary copy may be considerably different from that of the original document. However, in the range of a limited color tone, if a better color balance adjustment is performed, the variation of the color tone can be minimized.
Conventionally, the color balance adjustment is performed by referring to a copy obtained in a certain color balance in a manner of so-called cut and try. In this case, the scanning operation of the document is repeated by a number of times which is a product of a number of times of the color balance operation needed for obtaining a desired color copy and a number of the printing colors, and therefore, the color balance operation is time consuming and laborious.
The inventors of the present invention have proposed a color adjustment selecting method (referred to as a mosaic monitor method hereinafter) for decreasing time and cost required for the color correction in the U.S. patent application Ser. No. 321,405 as filed on March 10, 1989. In this mosaic monitor method, a part of a document (referred to as a specific area hereinafter) including a partial image for example a face of a person, for which the operator makes the color reproduction much particularly, is set by a specific area setting means, and then, image data of the specific area is stored in an image memory means. Next, the color adjustment is made for the image data read out from the image memory means with predetermined various color adjustment coefficients, and then, those image data are printed at different positions of the same copying paper in a mosaic-like pattern. Thereafter, the operator selects an image having a color balance nearest to that of a document or an image having a color balance most desirable for the operator among plural images of the specific area (referred to as mosaic monitor images hereinafter) which have been reproduced with different color balances, respectively. Thereafter, a copy of the whole area of document is produced based on the color adjustment coefficients of the mosaic monitor image selected. Thus, a copy of document having the most desirable color balance can be obtained easily.
However, there are various kinds of requests for the copying machine using the mosaic monitor method. For example, the operator may waver in selecting an image having the most desirable color balance, or he wishes to adjust the color balance more minutely. In such a case, in order to satisfy the above requests, it is necessary to print a larger number of mosaic monitor images on a copying paper. Furthermore, in the case that the operator has almost understood a change in the color balance of the image when the color balance is altered, or in the case that it is troublesome for him to determine an image having the most preferable color balance among the mosaic monitor images, it is necessary to print a smaller number of mosaic monitor images on a copying paper.